DE2922261A1 - ANTENNA SYSTEM - Google Patents

Description

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SIEMENS AKTIEITGESELLSCHAFT Our mark:

Berlin and Munich VPA 73 P 9SC9

Antenna system

The present invention relates to an antenna system for radio supply of tunnels, in particular of railway and road tunnels as well as mining tunnels and the like.

Radiation cables are used to provide radio coverage for road tunnels used because the radio signals cannot penetrate the tunnel walls. For this purpose are various Systems are known that use radiating coaxial cables to radiate or receive the RF signals.

So is from "PTT Technische Mitteilungen", issue 10/1977, Page 436 ff. Known that the coaxial radiation cables used for radio supply in road tunnels due to the special nature of their outer conductor must differ from ordinary coaxial cables. The outer conductor usually consists of a sol-

KIu 1 Shy / May 11, 1979

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Radiant cables for use in a motorway tunnel made of a perforated copper jacket or a copper jacket with a slit in the longitudinal axis of the cable. In the article mentioned the results from various tests are compiled, from which it can be seen that a cable type with Spiral slot has an extremely large longitudinal attenuation, another with a braid has a comparatively high coupling attenuation and is therefore unusable or unsuitable. Also another type with helically arranged Holes was eliminated because it did not produce better measured values at significantly higher production costs. After a cable type with a longitudinal slot, a cable type with holes in the longitudinal axis and a cable type with If other influences had been investigated, the cable type with holes in it became the cable type the longitudinal axis was chosen for series production.

Such coaxial cables consist of a metallic inner wire which is insulated from a dielectric material is, on the cylindrical surface of which the coating of a metallic outer conductor rests is in turn covered by an insulating and protective material. The dielectric material can for example consist of so-called foam polyethylene.

There are dielectric and insulating and protective materials that are flame retardant, but they are are combustible at the very high temperatures that can occur in a tunnel fire and can also melt relatively easily, so that there is a risk of a short circuit between the outer conductor and the inner wire is by no means excluded. Such materials are therefore not fireproof and therefore also not functionally reliable with regard to the conditions in a tunnel in the event of a fire. Right then but it is important that the police report about the

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~ ι VPA 78 ρ 9809 radio supply of the road tunnel to mobile police units with their own radio system and to motorists equipped with radio receivers via VHF.

The purpose of the present invention is to provide an inexpensive antenna system for radio coverage in tunnels that remains functional even if a fire breaks out.

The antenna system according to the invention is characterized in that the radiation element consists of electrically conductive Consists of wires that are held parallel and fixed in a fireproof manner.

Such a design of the antenna system has the advantage that the radiating element, with a suitable choice the diameter of the wires and their spacing from one another have sufficient radiation characteristics and no flammable dielectric and insulating materials are required.

In a further embodiment of the invention, the wires can be prestressed and, if necessary, an inner steel core and have a copper jacket, whereby the stress on the copper jacket when the Wires gets smaller.

The invention is explained below with reference to drawings

explained in more detail.
30th

Fig. 1 shows a schematic representation of a radio coverage antenna .

Figure 2 shows a piece of a radio coverage antenna suspended from the ceiling of the tunnel.

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/ VPA 78 P 9809 The radio supply system according to Fig. 1 has, for example, a first external antenna A1, which is mounted outside a tunnel at a secure reception and which via an input device ER, a central station ZS and a first amplifier V1 with a

first coupling circuit KS1 is connected, the output of which is connected via a first two-wire line ZL1 of length L1 to the input of a second coupling circuit KS2. The output of this second coupling circuit KS2 can be connected directly or underground via a second amplifier V2 stored in a disaster-proof room to the input of a third coupling circuit KS3, the output of which is connected to a second two-wire line ZL2 of length L2, at the end of which a receiving device or possibly another coupling circuit KS4 is connected. The mentioned two-wire lines ZL1 and ZL2 consist of two parallel wires, whose inner core is made of steel and whose outer sheath is made of copper. A wire available on the market, for example, has a wire cross-section with 70 % steel in the center and 30 % copper on the edge thereof. However, wires with other materials and / or a different composition are also useful.

The parallel wires DI and D2 are by means of supports ST1, ST2, ... made of a fireproof insulating material suspended from the corner of the tunnel, with the suspension it is provided that at a maximum temperature of e.g. 35 ° the lowest point of the cable does not exceed a specified distance from the tunnel ceiling. These supports ST1, ST2, ..., which are arranged at intervals of 15 m, for example, are used to keep them parallel and fastening of the wires and can be made of, for example, a refractory ceramic material. The cables

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VPA 78 P 9309 are biased so that there are two predetermined Temperatures results in only a minimal deviation due to bending due to expansion. Such two-wire line antenna sections could easily endure 1000 ° C heat during a fire for 5 minutes and 250 ° C for 20 minutes. in the In the event of a fire, the deflection of the cable wires can of course reach a relatively high value, However, what a perfect transmission of messages for the motorists and policemen in the police car not prevented. Any two police cars, one of which is one or both of them are in the tunnel, maintain a radio link between them.

At the exit of the tunnel, a second external antenna A2 can optionally be present, which has a secondary reception facility IIS is connected to the central station ZS. The central station ZS is also on the input side via one of the receiving device EE downstream Circuit HF with the output of the coupling circuit KS4 or the output of a coupling circuit KS (2n) if a number η of two-wire antenna sections ZL1, ZL2, ... Zln is present. Via a microphone M and a loudspeaker LP in the building of the central station ZS can send or receive reports to the police.

Fig. 2 shows a suspension in a tunnel, in which the ceiling DK is on transverse beams QB1, QB2, .... These Crossbars can have an unfavorable effect on the emission of electromagnetic waves. To such disturbances too To prevent this, the antenna system can also have one or more earthed wires D3, D4 parallel to the two have other wires DI, D2, which are also under a

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VPA 78 P 9809 preload can be mounted. In Fig. 2 are Still earthed, consisting of a refractory insulating material supports ES1 and ES2 shown, the Wires D1 and D2 form the two-wire line and the Wires D3 and D4 in the sense of an electromagnetic counterweight. are grounded. Of course are wires D3 and D4 are not absolutely necessary if there are no crossbars. For example Wires with a diameter of 6 mm used at a distance of 23 mm, supports ES1, ES2 at a distance of 15 mm are used and coupling circuits are installed at intervals of L1 = L2 = 500 m. Of course these values can also be chosen quite differently. In a very short tunnel, only one antenna section can be used sufficient.

Finally, it should be noted that when using a sufficient number of supports per unit of length, the pre-tensioning and / or the inner steel core of the wires ; can fall, especially if the grounded Wires can be mounted directly on the tunnel ceiling or on the crossbeams of the tunnel ceiling.

5 claims
2 figures

909850/0748

Claims (5)

Claims 1. Antenna system for the radio supply of tunnels, in particular of rail and road tunnels as well as mining tunnels, characterized that the radiating element consists of electrically conductive wires (D1, D2, ...) which are held in parallel and are fireproof. 2. Antenna system according to claim 1, characterized marked that at least one of the Wires (e.g. D3) is grounded. 3. Antenna according to claim 1 or 2, characterized marked that at least one of these Wires (D1, D2, D3, ...) is biased. 4. Antenna according to claim 3, characterized in that at least one of these Wires having an inner steel core and a copper jacket. 5. Antenna according to claim 4, characterized in that that existing supports (SSl, ES2, ...) are provided from a refractory insulating material with which all wires (D1, D2, ...) are kept parallel and that all wires (DI, D2, ...) are biased are and an inner steel core and a copper jacketL exhibit. 909 8 50/0 748 ORIGINAL INSPECTED